This invention relates to a plasma display panel (PDP) assembly used for a flat panel image display (wall-suspended TV) and the like.
A plasma display panel assembly generates ultraviolet rays by electrical discharge and irradiates the ultraviolet rays to phosphors for light emission. Therefore, it requires a system to release heat generated by the electric discharge. Particularly, as keeping high luminance for high definition necessitates more heat generation, it is conventional that a heat radiation plate is provided on a rear face of the panel assembly which, through a thermally conductive sheet, dissipates heat from the whole panel assembly and keeps the temperature even on the whole face.
FIG. 4 shows one example of a plasma display panel assembly mentioned above. The plasma display panel assembly 1 comprises a glass panel 2, an aluminum chassis 3 and a thermally conductive sheet layer 4 provided therebetween. The thermally conductive sheet layer 4, as shown in FIG. 5, comprises an adhesive double coated tape 5 and a thermally conductive sheet 6 provided therein, and the sheet layer is firmly attached to the glass panel 2 and the aluminum chassis 3 mainly by means of the adhesiveness of the adhesive double coated tape 5. The plasma display panel assembly 1 can dissipate the heat generated on the glass panel 2 through the thermally conductive sheet 6.
The plasma display panel assembly 1, however, has the glass panel 2 firmly attached to the aluminum chassis 3 so as to be integral with each other by the adhesive double coated tape 5 of the thermally conductive layer 4. Thus, it is difficult to separately collect the glass panel 2 and the aluminum chassis 3 at the end of their service life and the like, of the plasma display panel assembly 1, and further to dispose of the panel and chassis as separated garbage. Conventionally, the thermally conductive sheet 6 is formed mainly of a thermosetting silicone material, and the adhesive double coated tape 5 is formed mainly of a thermosetting acrylic or synthetic rubber material. Thus, for separate collection, the panel is heated to a temperature of not less than 300xc2x0 C. thereby to decompose or carbonize the thermally conductive sheet layer 4, or the panel is impregnated for a long time with a solvent or the like to swell the sheet. Therefore, it is desired to provide a panel assembly which maintains a good attachment and smoothly releases heat during operation, and which can be simply separated for collection when a disposal treatment and the like is necessary.
In view of the forgoing, it is an object of the present invention to provide a plasma display panel assembly which smoothly releases heat during operation and which is simply separated into a panel and a heat radiation plate.
In order to accomplish the above object, the plasma display panel assembly of the present invention comprises a panel, a heat radiation plate and a heat radiation adhesive sheet layer provided therebetween, wherein a heat radiation adhesive sheet for use in the heat radiation adhesive sheet layer is formed of a heat radiation adhesive composition containing the following components A to D.
(A) elastic styrene polymer
(B) adhesive-imparting agent
(C) oil
(D) thermal conductivity-imparting agent
The inventor of the present invention has made an intensive study to obtain the plasma display panel assembly which smoothly releases heat during operation and which is easily separated into a panel and a heat radiation plate. In the course of the study, it has been found that a heat radiation adhesive sheet is usable, which exhibits both a good adhesion and heat radiation and makes an easy separation possible, instead of an adhesive double coated tape which causes a problem in separating the panel and the heat radiation plate. As a result of reviewing various materials, when a heat radiation adhesive composition which comprises an elastic styrene polymer (component A), an adhesive-imparting agent (component B), an oil (component C) and a thermal conductivity-imparting agent (component D), is used as a material for formation of the heat radiation adhesive sheet, the sheet exhibits both a good adhesion and heat radiation at a temperature of xe2x88x9220 to 100xc2x0 C. during operation. Further, at a temperature of 101 to 120xc2x0 C., a little greater than 100xc2x0 C., the sheet is softened and fused for an easy separation. Thus, the inventor has attained the invention. Moreover, the heat radiation adhesive sheet formed of the heat radiation adhesive composition is solvent-soluble, which enables the display panel assembly to be separated into the panel and heat radiation plate by use of a solvent.
Particularly, when the content of each component in the heat radiation adhesive composition is in a specific range, a more preferable result can be obtained. When the elastic styrene polymer has a glass transition temperature within a specific range, a more preferable result can be obtained. Further, the use of a specific adhesive-imparting agent, oil, thermal conductivity-imparting agent leads to a more preferable result.